Shunt reactors, also known as compensation choke coils, are sufficiently familiar to the expert from the prior art and are in that case focused on medium-voltage and high-voltage mains for improvement of stability and economy of energy transmission systems. They essentially comprise a coil with at least one winding and an iron core displaceable between the windings of the coil for controlling inductance. These apparatuses from energy technology provide compensation for the capacitive reactive powers of transmission lines, particularly in lightly loaded or idle running transmission mains. Shunt reactors reduce mains-frequency over-voltages in the case of sudden drop in load or transmission mains in idle running. In a test system for a high-voltage apparatus a compensation choke coil represents an inductance to be checked.
The high-voltage test checks whether the compensation choke coil was correctly produced in terms of quality. In that case, a so-called surge voltage check has in principle the purpose of simulating transient over-voltages in three-phase mains by artificially generated pulse-like surges. A substantially more wide-ranging area is represented by tests with alternating voltage. The test object is in that case acted on by an alternating voltage. In this way it is possible, for example, to check the linearity of the compensation choke coil, its vibration and noise behavior, or temperature coefficients. Further significant elements are loss-power measurement and induced voltage testing by partial discharge measurement. The last-mentioned test delivers a decisive statement about the quality of the high-voltage insulation of the compensation choke coil.
The requirements, forms of voltage and determination of the parameters thereof are defined in IEC 60060-1, IEC 60076-3 and IEC 60076-6.
A test system known from the prior art for shunt reactors such as defined by the preamble of the applicable main claim is shown in FIG. 1. This test system is particularly suitable for testing shunt reactors and comprises a motor-generator set 1 electrically supplied by a supply source 2. Within the test system, the motor-generator set 1 has the task within the test system of adapting and regulating the frequency and voltage for the test system. As an alternative to the motor-generator set it is also possible to provide a frequency converter 3 connected by the inputs thereof with an energy source 2, for example the power mains. The outputs of the motor-generator set 1 or alternatively of the frequency converter 3 are in that case connected with the primary 4.1 of a test transformer 4. A compensation unit, here a variable capacitor 5, is interposed in the connecting line between the outputs of the motor-generator set 1 or of the frequency converter 3. The actual test object, namely the shunt reactor, shown in the electrical circuit diagram as an inductor, is connected with the secondary 4.2 of the test transformer. In order to reduce the voltage at the test object 6 to measurable values, a voltage divider 7 is provided between the test object 6 and the secondary 4.2 of the test transformer 4 that is connected with an unillustrated evaluating unit. All these mentioned components of a test system known from the prior art for shunt reactors have been known to the relevant expert for decades and, for example, available from the applicant as a test system for a high-voltage apparatus.
In order to be able to test shunt reactors of very high power of, for example, 110 MVA or thereabove it is necessary in the case of the test system known from the prior art to provide a test transformer with equally large electrical parameters, since the test transformer has to be designed for the maximum test voltage. The motor-generator set, which together with the energy source is constructed for electrical power supply of the test transformer, similarly has to be designed for the maximum test voltage. The costs of the test system are essentially determined by the electrical dimensioning of the test transformer. A test transformer designed in that way with an electrical power of up to 110 MVA in that case costs some millions of euros and in addition due to its mass is no longer movable by a crane.